Lecture #33: Upper GI Histology II

Question 1

What is the overall structure of gastric glands?

Answer 1

• simple branched tubular glands
• narrow isthmus opens into bottom of a gastric pit
• fundus (base) of the gland extends into the lamina propria
• cell of the gastric glands:
  
  • mucous neck cells
  • stem cells in neck
  • chief cells (zymogenic cells)
  • parietal cells (oxyntic cells)
  • enteroendocrine cells (APUD cells)
    
    • amine precursor uptake and decarboxylation

Question 2

What do mucous neck cells of gastric glands secrete?

Answer 2

soluble mucous

Question 3

Which cells, found in the neck of the gastric gland, replace other cells of the gastric pit?

Answer 3

Stem Cells

Question 4

What do Chief cells (zymogenic cells) of gastric glands secrete?

Answer 4

pepsinogen

Question 5

What do Parietal cells (oxyntic cells) of gastric glands manufacture and secrete?

Answer 5

• Manufacture -> HCl
• Secrete -> intrinsic factor

Question 6

What are enteroendocrine cells (APUD cells) of gastric glands and what do they secrete?

Answer 6

• small cells with secretory vesicls polarized toward basal surface in proximity to blood vessels
• produce:
  
  • peptide hormones
  • serotonin
• diffuse neuroendocrine cells that secrete hormones

Question 7

What are the characteristics of a parietal cell found in gastric glands?

Answer 7

• unique cell of the gastric glandj
• large pyramidal shaped, eosinophilic cell
• produces HCl and gastric intrinsic factor
• generates hydrogen ion from carbonic acid similar to osteoclast
• prominent intracellular canaliculi lined by microvilli
• tubulovesicle pools are part of exocytosis-endocytosis function

Question 8

True or False:

Parietal cells henerate hydrogen ions from carbonic acid similar to osteoclast.

Answer 8

True

Question 9

Which ions are actively transported into the lumen of the canaliculus of parietal cells?

Answer 9

Cl-, H+, and K+

*the K+ ion is the recycled back into the cytoplasm*

Question 10

When identifying between parietal and chief cells in a histomicrograph, which one appears eosinophilic?

Answer 10

parietal cell

Question 11

List the major structural featrues that increase surface area for absorption in the G.I. tract.

Answer 11

• length of small and large intestine
• Plicae circulares (valves of Kerckring)
• Villi
• Microvilli

Question 12

What are the 3 orders of folding that increase surface area in the small intestine?

Answer 12

1. Plicae
2. Crypt-villus System
3. Microvilli

Question 13

What are plicae in the small intestine?

Answer 13

these are folds of the mucosa, each with a submucosal core

Question 14

Describe the histology of the crypt-villus system.

Answer 14

• each villus contains a core of lamina propria
• the crypts etend down between the villi below the bases of the villi
• crypts and villi constitute glands of the small intestine
• the wall of villus is composed of a simple columnar epithelium with goblet cells
• each villus contains a capillary plexus
• each villus contains a blind-ending lymphatic referred to as a lacteal

Question 15

What type of epithelium makes up the wall of the villus in the crypt-villus system of the small intestine?

Answer 15

simple columnar epithelium with goblet cells

Question 16

Describe the fine structure of a microvillus.

Answer 16

• covered with glycoprotein and glycocalyx (glycolipid coat)
  
  • glycocalyx contains an array of brush-border enzymes:
    
    • maltase
    • sucrase
    • isomaltase
    • lactase
    • lipase
    • peptidases
    • produced by small intestinal epithelial cells
  • bundles of actin filaments within microvillus is covered by a formin cap
• supported by core of actin microfilaments
  
  • actin filaments are tied to terminal web intermediate filaments (cytokeratins via spectrin fibrils
  • actin filaments are bound to plasma membrane covering villus via membrane-linking proteins
    
    • myosin I and calmodulin
  • actin filaments are bound to each other via actin corss-linking proteins
    
    • villin and fimbrin

Question 17

Which 2 actin cross-linking proteins bind actin filaments to each other?

Answer 17

• villin
• fimbrin

Question 18

Which 2 membrane-linking proteins bind actin filaments to the plasma membrane covering the villus?

Answer 18

• myosin I
• calmodulin

Question 19

Which protein binds actin filaments to terminal web intermediate filaments (cytokeratins)?

Answer 19

spectrin fibrils

Question 20

What kind of cap covers the bundles of actin filaments within the microvillus?

Answer 20

formin cap

Question 21

What glycolipid coat covers microvilli in the small intestine?

Answer 21

Covered with glycoprotein and glycocalyx (glycolipid coat)

Question 22

What brush-border enzymes are contained within the glycocalyx?

Answer 22

• maltase
• sucrase
• isomaltase
• lactase
• lipase
• peptidases

Question 23

True or False:

The crypts, of the crypt-villus system in the small intestine, extend down between the villi below the bases of the villi.

Answer 23

True

Question 24

Do crypts and villi constitute glands of the small intestine?

Answer 24

Yes

Question 25

Look at micrographs in lecture #33 and identify:

• gastric pit
• gastric gland
• fundic portion of stomach
• parietal cells
• chief cells